During printed circuit board (PCB) manufacture, holes are typically drilled into the PCB. These holes may be used for the insertion of through-hole-component leads or may be used as “vias” to connect board layers.
The PCB has an exposed copper surface. Since copper is a very soft metal, the copper tends to burr if it is drilled without adequate support. Current methods of avoiding or suppressing burrs during the PCB drilling process involve stacking the PCB on a backup material, typically constructed of Melamine or hard-coated high-density fiberboard (HDF). The top side of the PCB is covered with an aluminum entry, which is often a sheet of aluminum approximately 150 microns to 250 microns in thickness. This technique has many drawbacks. For example, in some instances, while an operator is placing the PCB on the backup material or placing the aluminum entry material on top of the PCB, debris may become trapped between the PCB and either the backup material or the aluminum entry material. This debris may create a gap between the PCB and the backup material or aluminum entry material and the gap may allow a burr to be formed.
Gaps between the PCB and the backup material or the aluminum entry material may also exist if the PCB is not perfectly flat. For example, a warped PCB may create such gaps, allowing burrs to form during drilling.
In some instances, burrs may be pushed back into their associated hole so that the burr height of the burr (i.e., the amount by which the burr extends over the PCB) is reduced or eliminated. However, pushing the burr back into the hole can result in an undersized hole. This can cause a PCB to be rejected, resulting in scrapping of the PCB.
Furthermore, the back-up material that is commonly used for burr suppression is a coated wood core back-up material which is relatively expensive.
Thus, there is a need for improved methods and materials for suppressing burrs during PCB manufacture.
Like reference numerals are used in the drawings to denote like elements and features.